This application is based on and claims priority under 35 U.S.C. xc2xa7 119 with respect to German Application No. 100 38 848.5 filed on Aug. 4, 2000, the entire content of which is incorporated herein by reference.
The present invention generally relates to bearings. More particularly, the present invention pertains to a bearing ring having a track for retaining rolling bodies or a sliding surface, a method for manufacturing such a bearing ring, and a roller or plain bearing that includes such a bearing ring.
Many different types of bearing rings are known and can be produced in a variety of different ways. As a general rule, the production techniques used to form a bearing ring become more complex and expensive as the need for resistance to deformation in the bearing ring increases. The resistance to deformation in the area of the track or sliding surface of the bearing ring has an especially significant effect on the technical qualities of the bearing for which the bearing ring is produced. It is desirable that the diameter of the track or the sliding surface be kept as exact as possible with respect to both its absolute value and possible relative deviations, i.e., with respect to its roundness. One problem with this is that although the criteria of the shaving soft-processing of the bearing ring can be met at acceptable costs, the necessary subsequent hardening process causes deviations in the dimensions due to a thermal delay of the bearing ring. To fulfill the high precision requirements, it is therefore usually necessary after the hardening to carry out a shaving hard-processing of the bearing ring until the desired final dimensions are achieved. However, this hard processing is relatively complex and expensive.
DE 34 09 247 A1 describes a method for producing bearing seats with accurately positioned axes in light-alloy die castings in which needle sleeves are pressed into calibrated sinter parts. DE 21 17 018 C2 describes a hardened bearing sleeve that is pressed into a non-hardened outer collar. The two-piece bearing ring that is manufactured according to this method is pressed into a mold with the help of a needle, whereby the outer diameter of the bearing ring is calibrated by high-pressure molding.
In light of the foregoing, a need exists for a bearing ring that is able to fulfill the very high requirements of relatively precise or exact dimensioning in the area of its track or sliding surface without being excessively expensive.
It would also be desirable to provide a method of manufacturing such a bearing ring that does not entail the same complex and expensive processing as the known methods mentioned above.
According to one aspect of the invention, a bearing ring is designed as a two-piece bearing ring in the radial direction and includes a first ring part and a second ring part that are arranged concentrically to one another. The first and second ring part are pressed together in such a way that the peripheral surface of the first ring part is plastically molded into the peripheral surface of the second ring part through an axial flow forming process.
The materials used for the first and the second ring part are preferably of different hardness, with a material of greater hardness being used for the first ring part.
If the bearing ring is an outer ring, the first ring part or the second ring part can advantageously be provided with a flange that makes it easier to secure the bearing ring during subsequent installation.
In an axial portion of the peripheral surface of the first ring part that butts against the second ring part, the first ring part deviates from a cylindrical shape in the direction of a reduction of the cross-section of the first ring part. This axial portion is adjacent to the front of the first ring part. This yields an extremely intimate connection between the two ring parts so that the ring parts permanently maintain the shape they are given at the time they are joined.
This bearing ring construction is quite useful and entails advantages in the manufacture of the bearing ring while also ensuring that the two ring parts are permanently joined. The first and second ring parts are pressed together so that the second peripheral surface of the first ring part and the first peripheral surface of the second ring part lie against one another, with the first peripheral surface of the first ring part and the second peripheral surface of the second ring part forming the peripheral surfaces of the resulting bearing ring.
The production technique in accordance with the present invention involves the first ring part being first pressed into a pre-determined shape by way of a first tool in the area of its first peripheral surface, with the first ring part then being pressed concentrically against the second ring part with the help of this first tool. During this pressing, the second ring part is supported by a second tool to prevent distortion of the second ring part in the area of its second peripheral surface. In the area of the first peripheral surface of the second ring part, the contour of the second peripheral surface of the first ring part is plastically molded into the first peripheral surface of the second ring part through axial flow forming.
One advantage associated with this process of joining the first and second ring parts in accordance with the present invention is that the bearing ring produced in this manner has a high-precision circular cross-section in the area of its track or sliding surface.
To effect or produce axial expansion of the second ring part, an overlap between the first ring part and the second ring part is preferably utilized. This radial overlap is chosen to be at least 100 xcexcm. More specifically, the radial overlap is selected to correspond to the maximum thickness of the wall of the second peripheral surface of the first ring part plus at least 50 xcexcm. Through the axial flow forming, the wall thickness of the second ring part is reduced by 5% to 20%, preferably 10% to 18%. More preferably, the wall thickness of the second ring part is reduced by approximately 12%.
In the manufacture of an outer ring, the first tool is shaped as a solid cylinder, and in the manufacture of an inner ring, the first tool has a cylindrical bore. Each second tool is molded complementary to the first tool, and its measurements deviate from the first tool by the thickness of the wall of the bearing ring to be produced.
According to another aspect of the invention, a roller bearing or plain bearing includes the combination of an inner ring and an outer ring. At least one of the inner ring and the outer ring includes a first ring part having a first peripheral surface forming a track or sliding surface and a second peripheral surface, and a second ring part having a first peripheral surface and a second peripheral surface. The second ring part is positioned concentrically to the first ring part. The first ring part and the second ring part are pressed together, with the second peripheral surface of the first ring part being plastically molded into the first peripheral surface of the second ring part through axial flow forming of the second ring part.